The trypanocidal value of liposomal diminazene was examined. Three hundred mice were divided randomly into six groups of 50 mice each. Groups 1, 2 and 3 were pretreated 2 h before Trypanosoma brucei evansi challenge with 0.2 ml saline solution, 0.2 ml diminazene solution (5 mg ml-1) and 0.2 ml liposomal solution (5 mg diminazene per ml), respectively. Mice in Group 1 all died within 6 days, 33 in Group 2 and four in Group 3 died within 15 days after challenge, respectively. Groups 4, 5, and 6 were treated 4 days after T. b. evansi challenge with 0.2 ml saline solution 0.2 ml diminazene solution (5 mg ml-1) and 0.2 ml liposomal solution (5 mg diminazene per ml), respectively. Mice in Group 4 all died within 6 days, 19 in Group 5 and two in group 6 died within 15 days after challenge, respectively. The remaining mice survived for more than 30 days, were symptom-free and behaved normally. No adverse effects associated with treatment were noted.